I'm on United from SFO to Providence with a stop for my connecting flight at Newark, NJ. United all the way. Seems to me the last time I flew through Newark, they required I go through security again. Is that common practice at Newark?
No - but if your arriving and departing terminal are different, you have to leave the secure area to go to the other terminal and there go back in through security.
Or if you get lost and wander out accidentally, you would have to go back in again. Signage might well be mediocre enough to support the latter.